1. Field of the Invention
The present invention relates to an image stabilizer which is incorporated in an optical device such as a camera or binoculars.
2. Description of the Related Art
Optical image stabilizers (shake reduction systems/anti-shake systems) prevent (reduce) image shake of an object image formed at a focal plane by moving a part of an optical system relative to an optical axis thereof so that the part of the optical system shifts from the optical axis in accordance with the direction and the magnitude of vibration (shake) applied to the optical device in which the image stabilizer is incorporated. Such optical image stabilizers can be broadly divided into two types: a type of image stabilizer which swings an image-stabilizing optical element about an axis positioned away from the optical axis of the optical system, and another type (X-Y stage type) of image stabilizer which moves an image-stabilizing optical element in two directions orthogonal to each other. The latter type has the advantage that the image stabilizing optical element can be moved precisely in directions to cancel image shake; however, since there is a possibility of the driving mechanism for the image-stabilizing optical element becoming damaged when the optical device in which the image stabilizer is incorporated is not in use if the image-stabilizing optical element accidentally moves, the image stabilizer is usually provided with a lock device for the image-stabilizing optical element. As examples of such a lock device, two types of lock devices are known in the art: an electrical lock device which continuously supplies a driving signal to a drive source having a motor and/or an actuator to hold the image-stabilizing optical element at a predetermined position, and a mechanical lock device which mechanically locks the image-stabilizing optical element. The former lock device is seldom used because it consumes a large amount of power, which is unsuitable especially for an optical device using battery as a power source. An example of the latter lock device has been proposed in, e.g., Japanese unexamined patent publication H05-100280. This mechanical lock device is provided with a lock mechanism which is actuated in association with the motion of a retractable lens barrel between the fully retracted state and a ready-to-photograph state thereof. However, this conventional mechanical lock device requires such a lock mechanism to be provided as a separate mechanism, which becomes a cause of an increase in size of the image stabilizer.